1. Technical Field
The present invention relates to a method of manufacturing a substrate having periodically poled regions and, more particularly, a method of manufacturing a substrate having periodically poled regions, capable of suppressing a variation of a periodic structure caused due to the substrate and also attaining stable characteristics particularly even when a stoichiometric lithium tantalite substrate is used.
2. Related Art
A periodic electrode is formed on a surface of a lithium niobate substrate (CLN substrate) or a lithium tantalate substrate (CLT substrate) with a congruent (congruent melting) constitution and also a plane electrode is formed on a rear surface thereof, and then periodically poled regions are formed by applying the DC voltage in excess of the inverted voltage value (the voltage value at which the inverted current starts to flow) between these electrodes (see Japanese Patent No. 3059080 ([0040] to [0047])).
As mentioned above, the periodically poled regions are formed on the substrate by applying the DC voltage in excess of the inverted voltage value between these electrodes.
However, in the periodic structure of the periodically poled regions formed in this manner, there existed the problem such that a variation of the periodic structure is caused due to the substrate. In particular, in the recently developed stoichiometric lithium tantalite substrate, there existed the problem such that a variation of the periodic structure becomes large and thus stable characteristic cannot be obtained.